The purpose of this proposal is to determine a vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOSS) have a role in endotoxin-induced septic shock. Experiments will focus on the relationship between cardiopulmonary collapse and production of VIP, NOS, nitric oxide (NO), cAMP and cGMP during septic shock. Specific aims of this proposal are: #1 To determine if VIP increased during septic shock and whether there is a concomitant increase in NOS production during septic shock. Two hypotheses will be tested in specific aim 1: a) VIP and NOS are produced during septic shock with concomittant elevated levels of cAMP and cGMP and b) inhibitors of these compounds should attenuate the response seen during septic shock and the production of VIP, NOS, cAMP, and cGMP; #2. to test if endotoxin mediates the direct release of VIP and NOS, and the biosynthesis of cAMP and cGMP from endothelial, smooth muscle, mononuclear and polymorphonuclear cells. We hypothesize that each cell type stimulates the production of VIP and NOS when exposed to endotoxin and other mediators; and #3. To determine if cell to cell interactions must occur between activated phagocytes (monocytes, macrophages, determine if cell to cell interactions must occur between activated phagocytes (monocytes, macrophages polymorphonuclear cells), endothelial and smooth muscle cells to produce VIP and NOS with subsequent biosynthesis of cAMP, NO and cGMP. Seven protocols have been designed to accomplish the 3 specific aims. Protocol (a) is designed to infuse endotoxin and specific stimulators of white blood cells and soluble granulate cyclase to induce a specific response and production of VIP, NOS, cAMP and cGMP (there will be 3 controls groups, one each consisting of injections of VIP, L- arginine, and saline), and (b) will employ the use of specific inhibitors of endotoxin, VIP, and NOS. To accomplish specific aim 2, a cell culture system will be used to determine if macrophages, polymorphonuclear leukocytes, vascular endothelial and smooth muscle cells, each as individual agents, stimulate the production of VIP and NOS when exposed to endotoxin and others mediators. Specific aim 3 deals with cell to cell interactions between activated phagocytes, endothelial and smooth muscle cells and requires 4 experiments to accomplish this task. Each cell type will be grown alone and then in combination with others to ascertain if there are specific cell to cell interactions needed to produce VIP and NOS or amplify the process. In situ hybridization and characterization of receptor sites will be performed to accomplish specific aims 2 and 3. These experiments will be performed in the Wexner Institute for Pediatric Research which has an 18,000 AAALAC approved vivarium and is fully staffed.